The potential of triple-quantum procedures for imaging sodium nuclei for which the correlation time can be longer than the Larmor period in-vivo has been pursued. ([See, e.g., R. Kemp-Harper, P. Styles, S. Wimperis, Three-Dimensional Triple-Quantum-Filtration Na NMR Imaging, J Magn Reson 108 (1995) 280-284; R. Kalyanapuram, V. Seshan, N. Bansal, Triple-Quantum-Filtered Na Imaging of the Dog Head In Vivo, J Magn Reson Imag 8 (1995) 1182-1189; R. Reddy, E. K. Insko, J. S. Leigh, Triple quantum sodium imaging of articular cartilage, Magn Reson Med 38 (1997) 279-284; A. Borthakur, I. Hancu, F. Boada, G. Shen, E. Shapiro, R. Reddy, In vivo triple quantum filtered twisted projection sodium imaging of human articular cartilage., J Magn Reson 14 (1999) 286-290; I. Hancu, F. E. Boada, G. X. Shen, Three-Dimensional Triple-Quantum-Filtered Na Imaging of In Vivo Human Brain, Magn Reson Med 42 (1999) 1146-1154; and G. LaVerde, E. Nemoto, C. A. Jungreis, C. Tanase, F. E. Boada, Serial Triple Quantum Sodium MRI During Non-human Primate Focal Brain Ischemia, Magn Reson Med 57 (2007) 201-205). For example, a conventional implementation of a triple-quantum-filter (TQF) can rely on three hard pulses 111, 112, 113 with one additional hard refocusing pulse 114 between the first pulse 111 and the second pulse 112, as illustrated in FIG. 1A, which is an exemplary illustration a pulse sequence 110 and coherence-transfer-pathway diagram 115 for triple-quantum-filtration generated using a TQF procedure as described in, e.g., G. Jaccard, S. Wimperis, G. Bodenhausen, Multiple-quantum NMR spectroscopy of s=3/2 spins in isotropic phase: a new probe for multiexponential relaxation., J. Chem. Phys. 185 (1986) 6282-6293, and R. Reddy, M. Shinar, Z. Wang, J. S. Leight, Multiple-Quantum Filters of Spin-3/2 with Pulses of Arbitrary Flip Angle, J Magn Reson, Series B 104 (1994) 148-152. For example, these publications indicate that the sequence can employ a 180-refocusing pulse 114 which can provide B0 stability, but at a cost of increased SAR requirements. If appropriate phase-cycling procedures (as described in, e.g., such references) can be performed, the four coherence-transfer pathways contributing to the TQF signal can add-up to produce a relatively high signal-to-noise ratio (SNR). However, it is likely that a high efficiency of such procedure can not be achieved in in-vivo applications at relatively high magnetic fields (e.g., greater than or equal to about 3.5 Tesla, such as 7 Tesla), which can be due to specific absorption rate (SAR) limitations counteracting gains offered by high signal levels at the relatively high fields. In addition, in such implementations of TQF, transmitted B1-field inhomogeneities can introduce a relatively strong modulation in obtained images which can be difficult to correct in post processing. (See, e.g., I. Hancu et al., supra.; and S. P. Brown, S. Wimperis, NMR measurements of spin-3/2 transverse relaxation in an inhomogeneous field, Chem Phys Lett 224 (1994) 508-516).
A three-pulse TQF was likely therefore used by another exemplary procedure which can be performed without employing a refocusing pulse, such as described in, e.g., I. Hancu et al., and illustrated in FIG. 1B. For example, FIG. 1B shows an exemplary illustration a pulse sequence 120 and coherence-transfer-pathway diagram 125 for triple-quantum-filtration using three hard pulses 121, 122, 123. (See, e.g., I. Hancu et al., supra.; G. LaVerde et al., supra.; and C. Tanase, F. E. Boada, Triple-quantum-filtered imaging of sodium in presence of inhomogeneities, J Magn Reson 174 (2005) 270-278). Instead of using a refocusing pulse, the B0 stability can be provided by particular phase-cycling and post processing. (See, e.g., C. Tanase et al., supra.). The procedure described in, e.g., I. Hancu et al. can potentially offer a relatively simple B1-correction in post-processing and reduce the energy deposits in the body/sample associated with the filter use, and thereby likely making it potentially appealing for use in certain in-vivo applications. However, a disadvantage of the sequence 120 design can be an increased sensitivity to B0 inhomogeneities. (See, e.g., R. Reddy et al, supra.; C. Tanase et al., supra.; and J. M. Zhu, I. C. P. Smith, Selection of coherence transfer pathways by pulsed-field gradients in NMR spectroscopy., Concepts Magn Reson 7 (1995) 281-291). Such increased sensitivity can manifest itself as a signal loss which can arise due to a destructive interference between the different pathways contributing to the triple-quantum-coherence signal in the areas with B0 offsets, for example.
Additionally, because heretofore known clinical magnetic resonance imaging (MRI) systems likely cannot provide B0 homogeneity significantly better than about 0.5 ppm in-vivo, B0-correcting procedures of TQF sodium imaging can be of interest to anyone involved in the research and development of MRI systems, or the use thereof. One such B0-correcting procedure is described in, e.g., S. Wimperis, P. Cole, P. Styles, Triple-Quantum-Filtration NMR Imaging of 200 mM Sodium at 1.9 Tesla, J Magn Reson 98 (1992) 628-636, in which only two out of four contributing pathways can be selected. For example, FIG. 1C shows an exemplary illustration a pulse sequence 130 and coherence-transfer-pathway diagram 135 with gradient indication 136 according to a procedure described in such reference. As illustrated in FIG. 1C, the procedure described in this reference can employ three hard RF pulses 131, 132, 133, phase-cycling and gradients which can be for coherence pathway selection. This can reduce sensitivity of the procedure with respect to B0 offsets, but also reduce the measured signal and SNR-efficiency by a factor of about two. Another procedure that can be potentially used to resolve the problem is described in C. Tanase et al. For example, this publication describes a procedure which can be based on concurrent acquisition of the four signal constituents contributing to the triple-quantum signal and their appropriate recombination in post-processing with an ancillary B0-map. (Id.) However, because 24-steps can used to complete the TQF phase-cycle procedure described in this publication, the SNR-efficiency of the such procedure is likely also only about one half of a conventional procedure, such as described in, e.g., G. Jaccard et al. and R. Reddy et al., and herein above, and illustrated in FIG. 1A, for example.
Most of the damage to the TQF signal due to possible B0-offset is likely done during the creation time between the first and the second excitation-pulses. The procedure described in, e.g., S. Wimperis, P. Cole, P. Styles, Triple-Quantum-Filtration NMR Imaging of 200 mM Sodium at 1.9 Tesla, J Magn Reson 98 (1992) 628-636 can address this problem by dephasing two out of the four contributing pathways using a gradient pulse, while the procedures described in, e.g., Tanase and Boada can include extracting the four contributing signals and correcting for B0 in post processing. However, both of these approaches can lead to a loss of SNR efficiency.
Accordingly, there can be a need to address and/or overcome at least some of the above-described deficiencies and limitations, and to provide exemplary embodiments of arrangement and procedure according to the present disclosure as described in further detail herein.